Comparison of microcomputed tomography, cone beam tomography, stereomicroscopy, and scanning electron microscopy techniques for detection of microcracks on root dentin and effect of different apical sizes on microcrack formation.

The aim of the study was to compare different imaging methods in the diagnosis of microcracks on root dentin and to evaluate the frequency of dentinal microcracks observed after root canal preparation using the ProTaper Universal (PTU) system of different sizes. A total of 30 mandibular molars' mesial roots were scanned with microcomputed tomography (micro-CT) and cone beam computed tomography (CBCT) imaging methods before instrumentation. Root canal instrumentation was performed up to PTU F2 and F4 files. After instrumentation stages, the roots were scanned again with micro-CT and then with CBCT in same parameters. All roots were sectioned horizontally at 2, 4, 6, 8, and 10 mm from the apices of the specimens. The sections were imaged under a stereomicroscope. Finally, imaging of the sections was done by scanning electron microscopy (SEM). Statistical data analysis of instrumentation steps was performed using Friedman and Wilcoxon tests, and the data of imaging methods were analyzed using Kruskal-Wallis and Mann-Whitney U tests (p = .05). Instrumentation with the PTU system up to F2 and F4 files significantly increased the number of microcracks compared with preoperative samples according to micro-CT imaging (p < .05). For detecting microcracks on the root dentin, there were no statistically significant differences between micro-CT (43.9%) and stereomicroscopy (45.8%) (p < .05). SEM showed significantly higher percentage of microcracks (88.3%) (p > .05). No microcrack was observed using the CBCT method. There were no statistically differences between micro-CT and stereomicroscopy. SEM showed more dentinal microcracks while no microcrack was observed with CBCT.

Deionized water can substitute common bleaching agents for nonvital tooth bleaching when treated with non-thermal atmospheric plasma.

The bleaching efficacy of common bleaching agents and deionized water treated with non-thermal atmospheric pressure plasma in the pulp chamber for nonvital tooth bleaching was evaluated. A total of 120 extracted human maxillary first incisors were stained using human blood. Teeth were randomly divided into eight groups (n = 15). In the first four groups, teeth were bleached using 35% hydrogen peroxide gel, 37% carbamide peroxide gel, 2:1 (w/v) sodium perborate paste, and deionized water for 30 min. In the remaining groups, bleaching agents were treated with non-thermal atmospheric plasma for 5 min inside the pulp chamber. Overall color changes (∆E) were determined using Commission Internationale de L'Eclairage Lab Colour System. The plasma-assisted tooth bleaching has not increased tooth temperature beyond 37°C. Bleaching efficacies of bleaching agents were significantly improved when treated with non-thermal atmospheric plasma compared to their application (P < 0.05). A remarkable bleaching effect was obtained when bleaching agents were substituted with water and when treated with non-thermal atmospheric plasma. Non-thermal atmospheric plasma treatment could be a novel tool for activation of bleaching agents in the pulp chamber for nonvital tooth bleaching procedure. Moreover, water could be used as a novel bleaching agent when treated with the non-thermal atmospheric plasma to eliminate possible risks which might arise from peroxide-containing agents.

Effects of different instrumentation techniques on calcium hydroxide removal from simulated immature teeth.

The aim of this study was to evaluate the effectiveness of endodontic instrument systems in the removal of calcium hydroxide [Ca(OH)(2)] from simulated immature teeth. The root canals of 106 human single-rooted teeth were shaped with ProTaper rotary files up to an F5 file size. Simulation of roots with immature apices was carried out using size 4 green 1.5-mm diameter Unicore drills. A non-setting Ca(OH)(2) was injected into each root canal and inserted into the working length using lentulo spiral, after which cotton pellets were placed over canal orifices. The apical and coronal side of the roots were then sealed with glass ionomer cement and light cured. Specimens were stored in distilled water for 3 months at 37 °C. After 3 months, the temporary coronal seal was removed and the samples were randomly divided into five experimental groups according to the method used for Ca(OH)(2) removal (ProTaper, Reciproc, OneShape, WaveOne, and Manual) (n = 20), one positive control group (n = 3) and one negative control group (n = 3). The amount of remaining Ca(OH)(2) in the canal walls was measured under a stereomicroscope at 30× magnification. The data were analyzed using Kruskal-Wallis test and Mann-Whitney U test at a significance level of 0.05. Positive and negative control groups were found to be statistically different from all other groups (p < 0.05). There were no significant differences among the ProTaper, Reciproc, OneShape, WaveOne, and Manual groups (p > 0.05). As a conclusion, none of the techniques completely removed Ca(OH)(2) from simulated immature teeth.